The invention relates to the use of an aluminum alloy as material for cathode foils in electrolytic capacitors.
Cathode foils in electrolytic capacitors are today mainly made of pure aluminum or aluminum-manganese alloys. It is also known that, in the case of cathode foils of Al-Mn alloys, an addition of copper increases the capacitance values achieved after etching. The addition of copper does, however, have a disadvantage with respect to the long term behavior of the capacitor as the copper oxide formed on etching dissolves in time in the electrolyte of the capacitor and precipitates again as metallic copper on certain parts of the capacitor. The said precipitated crystals of copper can lead to electrical discharges in the capacitor, which is thus prematurely rendered unusable.